This invention relates to chain links and chain link assemblies for conveyor chains and, more particularly, to an improved chain link assembly especially adapted for use in enclosed track-type conveyor chains.
Conventional enclosed track-type conveyors, which may be built into the floor of a plant or facility or supported overhead, usually include numerous curves, both horizontal and vertical. Conveyor chain used in such enclosed track environments includes support wheels rotatable in two planes, both horizontal and vertical, to both provide the main support for the conveyor chain within the track and to space the chain and keep it from binding within the track as it moves around the various curves. Such chain includes various links or link assemblies and must pivot or articulate around the curves. Typically, the vertical curves have a larger radius than the horizontal curves in such conveyor systems with the minimum radius being three feet for horizontal curves and five feet for vertical curves. Such radii require articulation through approximately 20.degree. for horizontal curves and 14.degree. for vertical curves.
Certain prior chain used in enclosed track environments utilized long support links for supporting the objects moved by the conveyor. Shorter connecting links provided the articulation between the longer links. The shorter connecting links supported the main chain support wheels while the longer links included the spacing wheels to prevent binding. One such prior chain included shorter connecting links formed from sintered, powdered metal and pivotally joined to one another. Although relatively strong in compression, the powdered metal links were found to be relatively weak in tension which is the most significant force applied to enclosed track-type conveyor chains. Accordingly, such chain links often broke under severe stress and uneven loading, were expensive to manufacture, and also had a tendency to wear heavily especially at the areas joined to the other links by chain pins or fasteners. Further, it was very difficult to plate such connecting links with non-corrosive metal to prevent corrosion as is required for use of such chain in food handling industries and other sanitary conditions.
Therefore, a need existed for an improved enclosed track-type conveyor chain and especially for a connecting link for use in such chain which would overcome the above problems and yet provide the necessary amount of articulation. A related but distinct chain link assembly and chain are disclosed in commonly assigned United States patent application Ser. No. 80,656, invented by Gerald W. Gurney and William Lanham, filed on even date herewith.